These words refer to an exact or approximate rendering of an original. Copy is the most general of these, applying both to exact and inexact renderings: a carbon copy of the letter; a Roman copy of the original Greek statue; manufacturers who mass-produce copies of Paris fashions; a poorly executed counterfeit copy . Duplicate and replica , by contrast, specifically stress the exactness of the copy . Duplicate may suggest an exact and valid replacement: applying for a duplicate of his lost passport. It may even refer more particularly to one of two identical things: sorting through his library for duplicates ; a frieze that is the duplicate of one on the front of the building. In less precise usage, the word may shade off in reference merely to things that resemble each other, or to an accurate copy ; an obelisk that is the duplicate of several in Egypt; a duplicate of the bill of lading. Replica , most precisely, refers to a copy made by the creator of the original: Rodin’s habit of making a number of replicas each time he cast a statue. As in this example, any sense of original and copy is obliterated. More loosely, however, the word is simply a more formal substitute for copy ; it may even be popularly understood to mean a rough approximation: a replica of what an Elizabethan theatre must have looked like. When replica is used in the sense of a small trophy held by a competitor instead of the original, there may not be any similarity between the two.

Though more formal, facsimile is almost as general as copy , since the degree of exactness is not specified. Often the word is used to indicate only a schematic approximation of an original: a contest anyone can enter by sending a soap wrapper or a reasonable facsimile thereof. Even in other uses, the word always suggests easily noticeable differences between original and the copy . Reproduction is also vague about the degree of accuracy implied. Sometimes the stress is on a close resemblance to the original: a remarkably skilful reproduction of the original painting. Often, however, the word may be used to suggest a simplified or less expensive version of a prototype: applauding hand-sewn showpieces that will deluge the country as machine-stitched reproductions . Model is unique among these words in specifically indicating an approximate rendering; the word suggests a schematic approximation, often of reduced scale, that may precede supersonic transport plane; a working model of the new turbine. The word, in any case, seldom suggests the kind of copy that could be mistaken for the original; a functional or illustrative mock-up is more often indicated: using models of the space capsules to show the manoeuvring involved in "docking" ?bringing them together in space.